The present invention relates to a manufacturing method for a semiconductor device, for example, using STI (Shallow Trench Isolation) for element isolation.
In recent years, with requirements of miniaturization and high functionality of electronic devices, STI has been used as an element isolation technique for improvement of device performance, such as miniaturization and higher performance.
Generally, STI is formed in the following way. First, a shallow trench is formed on a semiconductor substrate using a mask material such as a SiN film by RIE (Reactive Ion Etching) method. After an insulating material is embedded in the trench using HDP-CVD (High Density Plasma-Chemical Vapor Deposition) method, the trench is flattened using CMP (Chemical Mechanical Polishing) method. In addition, the mask material is selectively removed using hot phosphoric acid (H3PO4) solution to form STI. At this time, there is a height difference corresponding to the mask material between a formed STI surface and a semiconductor substrate surface.
Next, on the semiconductor substrate including the STI, a gate electrode material such as a polysilicon film and a gate side wall material such as a TEOS (Tetra Ethoxy Silane) film, a BSG film (boron-doped oxide film) and an SiN film are deposited and patterned to form a gate electrode. At this time, such materials remain on a STI side face at the height difference portion, which causes a low yield due to dust generation.
Accordingly, there has been known a method for forming a side face (height difference) of a protruding STI into a forward tapered shape to inhibit generation of etching residues during processing of a gate electrode or a gate side wall, as disclosed in claim 1 and a paragraph [0019] of Japanese Patent Application Laid-Open No. 2000-21967. However, processing of STI after removal of a mask material causes damage to a semiconductor substrate so that gate leak due to a crystalline defect may occur. Further, by only chamfering the side face, residues cannot be effectively removed.